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Hydroelectric
power was the largest source of renewable energy consumed
in the United States in 2002, accounting for 45% of all renewable
energy used.
Even so, only 2.7% of the overall
energy market for the US came
from Hydro-electric power.
The most common
type of hydroelectric power plant uses a dam on a river
to store water in a reservoir. Water released from the reservoir
flows through a turbine, spinning it, which in turn activates
a generator to
produce electricity. Hydroelectric power doesn't necessarily require a large dam.
Some hydroelectric power plants just use a small canal to channel
the river water through a turbine.
Small
run-of-the-river hydropower systems consist of these basic
components:
- Water conveyance—channel, pipeline, or pressurized pipeline
(penstock) that delivers the water
- Turbine or waterwheel—transforms the energy of flowing
water into rotational energy
- Alternator or generator—transforms the rotational energy
into electricity
- Regulator—controls the generator
- Wiring—delivers the electricity.
- Many systems also use an inverter to convert the low-voltage
direct current (DC) electricity produced by the system into 120
or 240
volts of alternating current (AC) electricity (alternatively you
can buy household appliances that run on DC electricity).
- Some systems also use batteries to store the electricity generated
by the system, although because hydro resources tend to be more
seasonal in nature than wind or solar resources, batteries may
not always be practical for hydropower systems. If you do use batteries,
they should be located as close to the turbine as possible because
it is difficult to transmit low-voltage power over long distances
Another type
of hydroelectric power plant— called a pumped
storage plant— can even store power. The power
is sent from a power grid into the electric generators.
The generators
then spin the turbines backward, which causes the turbines
to pump water from a river or lower reservoir to an
upper reservoir,
where the power is stored. To use the power, the water
is released from the upper reservoir back down into
the river or lower reservoir.
This spins the turbines forward, activating the generators
to produce electricity.
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